Blade-retention system for a blasting machine

ABSTRACT

A locking system for blasting machine blades is based upon locking members mounted in the spacers maintaining the relative position of axially spaced wheel discs receiving the blades in radial grooves. The blades extend radially beyond the periphery of the wheel discs, and have an offset engaging the peripheral surface to limit inward blade movement.

[15] 3,654,736 5] Apr.1l, 1972 De Groot [54] BLADE-RETENTION SYSTEM FORA BLASTING MACHINE [72] Inventor: John E. De Groot, Grand Rapids, Mich.

[73] Assignee: Benfur Engineering Company, Grand Rapids, Mich.

[22] Filed: Sept. 8, 1969 [21] Appl. No.: 856,079

[52] U.S.Cl ..51/9 [5 l Int. Cl. ..B24c 3/04 [58] Field of Search ..51/9

[56] References Cited UNITED STATES PATENTS 3,241,266 3/1966 Bowling..51/9 3,383,804 5/1968 I-laider ..51/9

Primary Examiner-Lester M. Swingle Attorney-Glenn B. Morse [5 7]ABSTRACT A locking system for blasting machine blades is based uponlocking members mounted in the spacers maintaining the relative positionof axially spaced wheel discs receiving the blades in radial grooves.The blades extend radially beyond the periphery of the wheel discs, andhave an offset engaging the peripheral surface to limit inward blademovement.

4 Claims, 12 Drawing Figures PATENTEDAPR 11 I972 3, 654. 736

sum 1 OF 2 I 7 INVENTO John E. DeGroo r Fig. 5 E

BLADE-RETENTION SYSTEM FOR A BLASTING MACHINE BACKGROUND OF THEINVENTION A blasting machine projects a stream of abrasive particlesaccelerated to high velocity by the action of a throwing wheel. Thiswheel has a general resemblance to a paddle wheel, and provision is madefor the injection of particles of abrasive material in the central areaof this wheel. Radially-arranged blades receive a flow of abrasiveparticles, and the rotation of the wheel generates the high velocity.The engagement of the abrasive particles with the blades producesextreme wear conditions, and the blades are normally manufactured fromcast alloyed material of extreme hardness. These blades are frequentlyreplaced, and are received within generally radial locating slots thatextend to the outer periphery so that the blades can be slid into andout of the machine. The relatively high centrifugal forces involvedrequire the provision of a reliable locking arrangement. Many of thesehave been devised, and are almost invariably based upon some sort oflocking member interengaging a portion of the blade with at least one ofthe wheel discs. Set screws having threaded engagement with the wheeldiscs are common, as well as spring clip arrangements of the type shownin Barnes, U.S. Pat. No. 2,8l9,562. An arrangement involving a moveablelocking member bridging across between the two wheel discs is shown inDe Groat et al., U.S. Pat. No. 3,352,064.

In addition to locking the blades against the action of centrifugalforce, it is also desirable to have some arrangement limiting the inwardmovement of the blade so that a new replacement blade can be slid intoplace with automatic positioning such that the locking system is inapproximate alignment for engagement. If this is not provided, theradial slots in the wheels will permit the blade to slide inwardly intothe central area of the wheel. This can be prevented, of course, bymanually holding the blade in approximately the correct radial positionwhile the locking system is interengaged. The requirement of this muchmanual manipulation is undesirable, and is preferably replaced by somepositive stop arrangement.

The principal problem encountered in the continued effective functioningof a blade-positioning system is the effect of the stream of abrasive.Moving parts tend to become jammed as abrasive particles work their wayinto the spaces between the moving surfaces. Another requirement of aneffective locking system is excessibility at the outer periphery of thethrowing wheel. These wheels are normally confined within a housing,with a small access door being provided for the changing of blades.Since the blades are slid out and inserted radially, the presence of thelocking system at the point of blade insertion is a distinct advantage.

SUMMARY OF THE INVENTION This invention provides a locking systemtransferring forces to the disc spacers, rather than directly to thediscs themselves. The spacers are positioned close to the back of theblades (the opposite surface from that receiving the stream ofabrasive), and a locking member mounted on the spacer is positioned toengage some sort of offset on the blade. The locking member may be inthe form of an end portion on a cantilever spring, the opposite endbeing secured to the spacer. Locking can also be accomplished by a cammounted on a rod arranged generally radially with respect to the wheel,the outer end of the rod being engageable with an actuating wrench. Afurther modification of the invention provides a locking action througha moveable plug mounted in the spacer, and engageable with a suitablerecess in the blade. These arrangements all have the advantage ofreducing the complexity of the wheel discs, and require no specialaccess openings in the housing. Special provision is made in thesemodifications for minimizing the effect of abrasive particles on theworking parts.

DESCRIPTION OF THE DRAWINGS In the drawings, FIG. 1 is a sectionalelevation through a blasting machine in which one embodiment of theinvention has been incorporated for retaining the blades in position.

FIG. 2 is a perspective view of one of the disc spacers of the assemblyillustrated in FIG. 1.

FIG. 3 is a perspective view on an enlarged scale one of the bladesshown in the FIG. 1 assembly.

FIG. 4 illustrates a modified form of the locking member from that shownin the FIG. 1 assembly.

FIG. 5 illustrates the form of locking member shown in the FIG. 1assembly.

FIG. 6 is a sectional elevation on the plane 6-6 of FIG. 7 perpendicularto the axis of rotation of the machine shown in FIG. 1, illustrating thelocking action in the FIG. 1 assembly.

FIG. 7 is a section on the plane 7-7 of FIG. 6.

FIG. 8 is a view on a plane similar to that of FIG. 6, but illustratinga modified form of the invention.

FIG. 9 illustrates a further modification of the invention, and is asectional view taken on a plane transverse to the blades and parallel tothe axis of rotation.

FIG. 10 is a view on the plane 10-10 of FIG. 9.

FIG. 11 illustrates a further modification of the invention, taken on aplane similar to that of FIG. 9.

FIG. 12 is a section on the plane 12ofFIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, theillustrated blasting machine includes a throwing wheel generallyindicated at 20 mounted on the shaft 21 for rotation within the bearingstructure 22. The throwing wheel 20 includes the discs 23 and 24 securedto the hub 25 by bolts as shown at 26 and 27. The disc 24 is the onlyone secured directly to the hub 25, with the discs 23 and 24 beingsecured with respect to each other by spacers as shown at 28 and 29.These spacers are of a channel-shaped configuration as shown in FIG. 2,being secured by the bolts 30 to the discs 23 and by the bolts 31 to thedisc 24. These bolts traverse the flanges 32 and 33, leaving the backportion 34 to serve the function of spacing the discs 23 and 24, andproviding a base for the locking system provided by this invention. Theremainder of the wheel structure shown in FIG. 1, including the abrasiveinlet 35, the abrasive impeller 36, and the control cage 37 are standardconstruction.

In the locking system shown in FIG. I, the spacers are provided with acentral opening 38 transversed by the cantilever leaf spring lockingmember 39. Blades are shown at 40 and 41 are received within the usualradial slots in the discs 23 and 24, and are spaced evenly around theperiphery of the wheel structure 20. These blades are each provided withshoulders as shown at 42 and 43 in FIG. 3, for engagement with theperipheral surfaces 44 and 45 of the wheel discs 23 and 24,respectively, to limit the inward movement of the blades, and minimizethe diameter of the discs for a given requirement of blade surface. Theinner extremity of the blade is beveled as shown at 46 in FIG. 3 forclearance with respect to the stream of abrasive induced by the adjacentblade at the relatively crowded space near the axis of rotation. Thisbeveled surface is utilized by the present invention additionally forassisting in the placement of a spring-biased locking member.

Referring to FIG. 6, the initial insertion of the blade takes place withthe bevel 46 entering the wheel at the opening of the slots. As theblade is moved to the right, as shown in FIG. 6, the surface 46 contactsthe locking member 47, which is a portion of a cantilever leaf springsecured to the back 34 of the spacer 28 by the bolt 48. Continuedmovement of the blade 40 to the right will induce upward deflection ofthe locking member 39 to the point that the portion 47 will ride overthe back surface 49 of the blade. The portion 47 will ultimately dropinto the recess 50, and the blade will then be locked against the actionof centrifugal force tending to move the blade back out to the left, asshown in FIG. 6. As the intensity of this force develops, the resilienceof tee spring 39 will permit the portion 47 to become crowded betweenthe righthand end of the recess 50 (as shown in FIG. 6) and the lefthandextremity of the opening 38 in the spacer.

The security of this arrangement can be increased by the use of themodified locking member shown in FIG. 4. The portion 51 of thismodification is relatively wider than the opening 38 in the spacer,which is slightly in access of the width of the portion 52, secured tothe spacer by a bolt such as the bolt 48 shown in FIG. 6. In theassembly of the unit shown in FIG. 4, the portion 52 is moved upwardthrough the opening 38, and then rotated down into position where thebolt 48 can be secured. In such an arrangement, the radial extend of theopening 38 can be much less than that illustrated in FIG. 6, since onlya sufficient gap is required to admit the portion 52, and permitrotation into the mounted position. The FIG. 4 lock requires clearancebetween the back of the blade and the spacer of at least the thicknessof the portion 51.

In the modification shown in FIG. 8, the channel-shaped spacer 53 isprovided with a hole in the back 54 slightly larger in diameter than thediameter of the wire of which the spring member 55 is formed. Thelocking action is provided by the end 56 which traverses the hole in theback 54, and enters an aligned recess in the blade 57. To increase theresilience of the spring, so that a heavier gage of wire may be used forgreater locking strength, it is preferable to incorporate a coil 58 ofone or two turns. This will increase the ability of the spring toaccommodate upward deflection to a sufficient extent to withdraw the end56 from the recess in the blade 57. The spring member is secured inposition by the bolt 59 engaging a loop 60. To avoid tendency fortightening of the bolt 59 to swing the spring across the surface of theback 54, it is preferable to incorporate a shield 61 having a portion 62engaging the outer end of the spacer 53 to prevent rotation of theshield as the head of the nut is turned.

Referring to FIGS. 9 and 10, the wheel discs 63 and 64 are separated bythe spacer block 65, which is secured in position by the bolts 66 and67. This spacer is mounted closely to the back of the blade 68, theposition of which is determined by the conventional slots in the discs63 and 64. A hole in a substantially radial direction through the centerof the spacer block 65 receives the rod 69 in rotatable relationship.The locking arm 70 is secured to the inner end of this rod, and swingsto and from a position engaging an aligned recess in the blade 68.Actuation of the cam is accomplished by a suitable wrench engaging thesquared end 71 of the rod 69, and it will be noted that this end isadjacent the outer periphery of the wheel where it will be exposed atthe point where the blade is withdrawn and inserted. If desired, acompression spring 72 can be incorporated as shown in FIG. to establishincreased resistance to rotation of the rod 69, or the opposite ends ofthe spring 72 can be secured, respectively, to the spacer 65 and the rod69 to affect a torsional bias tending to maintain the cam 70 inengagement.

The modification illustrated in FIGS. 11 and 12 provides a lockingaction through the plug 73, which is slidably mounted in a suitable borein the spacer block 74. This block maintains the spaced relationship ofthe wheel discs 75 and 76, and is located adjacent the position of theback of the blade 77. The spacer is secured to the wheel discs by boltsas shown at 78 and 79. A hole 80 in a generally radial direction is openat the outer extremity, and intersects the hole in which the lockingplug 73 is accommodated. Prior to the assembly of the plug 73 into thespacer block 74, the spring 81 and the ball 82 are inserted. The plughas a narrow waist 83 of a radius preferably somewhat greater than thatof the ball 82, and receives the ball under the pressure of the spring81 to maintain the relative position of the plug illustrated in FIG. 12.The head 84 of the plug may be engaged by the end of a screwdriver, withthe comer 85 of the spacer functioning as a fulcrum, to raise thelocking plug 73 a sufficient extent to withdraw it from the recess inthe blade 77 in which the lower end of the plug is received for lockingengagement. The conformation of the spacer block 74 and the orientationof the hole' 80, is such as to inhibit the inflow of abrasive particlesduring the operation of the machine. These particles have a direction ofmovement from right to left, as shown in FIG. 12, and the open outerextremity of the hole 80 will tend to provide a path of egress for anyparticles that find their way into such a position as to bind the motionof the locking plug.

I claim:

1. A system for locking the blades of a blasting machine, said machinehaving axially spaced discs separated by spacers and defining a throwingwheel normally mounted on a rotatable shaft, said discs havingsubstantially radial grooves receiving the edges of said blades, whereinthe improvement comprises:

locking means mounted on said spacers and engageable with said blades toprevent outward movement thereof, said spacers being provided withapertures disposed transversely with respect to an adjacent blade, andsaid locking means including a plug having a portion thereoftransversing said aperture and slideably mounted with respect to saidspacer, and having a head normally disposed on the opposite side of saidspacer from said blade.

2. A system as defined in claim 1, including detent means mounted insaid spacer and engageable with said plug to maintain the lockingposition thereof.

3. A system as defined in claim 2, wherein said detent means is mountedin a hole in said spacer open exclusively on the radially outermost facethereof, and intersecting a hole receiving said plug.

4. A throwing wheel for a blasting machine, said wheel having at leastone disc disposed with a peripheral edge, said disc being secured to ahub member and provided with radial grooves, said wheel also havingblades disposed with a portion of at least one edge thereof received inone of said grooves, said wheel also having locking means adapted tosecure said blades against the action of centrifugal force, wherein theimprovement comprises:

portions on said blades extending radially beyond said peripheral edgeof said disc, said blade portions having an offset engageable with saidperipheral edge to limit inward movement of said blades.

Patent No. 3,654,736 Dated Agril H, 1972 Inventor(s) John E. DeGroof Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

C o l u mn 1 i n e 2 8, c h a n 6 DeG rout to De G roof Signee andsealed this 6th day of March 1973. 1 1

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM PO-1050H0-69) USCOMM-DC 60376-P69 U S. GOVERNMENTPRINTING OFFICE T 1969 O366334

1. A system for locking the blades of a blasting machine, said machinehaving axially spaced discs separated by spacers and defining a throwingwheel normally mounted on a rotatable shaft, said discs havingsubstantially radial grooves receiving the edges of said blades, whereinthe improvement comprises: locking means mounted on said spacers andengageable with said blades to prevent outward movement thereof, saidspacers being provided with apertures disposed transversely with respectto an adjacent blade, and said locking means including a plug having aportion thereof transversing said aperture and slideably mounted withrespect to said spacer, and having a head normally disposed on theopposite side of said spacer from said blade.
 2. A system as defined inclaim 1, including detent means mounted in said spacer and engageablewith said plug to maintain the locking position thereof.
 3. A system asdefined in claim 2, wherein said detent means is mounted in a hole insaid spacer open exclusively on the radially outermost face thereof, andintersecting a hole receiving said plug.
 4. A throwing wheel for ablasting machine, said wheel having at least one disc disposed with aperipheral edge, said disc being secured to a hub member and providedwith radial grooves, said wheel also having blades disposed with aportion of at least one edge thereof received in one of said grooves,said wheel also having locking means adapted to secure said bladesagainst the action of centrifugal force, wherein the improvementcomprises: portions on said blades extending radially beyond saidperipheral edge of said disc, said blade portions having an offsetengageable with said peripheral edge to limit inward movement of saidblades.